1. Effective communication of a protocol has no relevance to its efficacy. So that's a plainly unscientific test of the 'truthiness' of anything.
2. No phenomenon ever, scientific or not, can be guaranteed to be stable in the face of all 'unknown' factors. They are unknown, you cannot make any statement about that.
I understand where you are coming from, but that puts you right in the middle of the philosophical quagmire mentioned in my earlier comment. If you mean 'variation in people performing the experiment' by those 'unknown factors' then essentially you are making the assumption that the people are not a factor that is expected to influence the result. As such, even the same team repeating the experiment would suffice. Anyway, you get the point.
It's a time tested heuristic. If a result cannot be communicated well enough for others to replicate or if it strongly depends upon local conditions (doesn't really matter which reason), we should either focus on something else or figure out why. If there is no independent replication, there is no chance to learn either of the above and no reason to have confidence we know what is going on.
I see no quagmire, it is all very straightforward. I will not believe my own results until others replicate them. Even once is not enough to hang my hat on. What alternative approach do you use to judge whether an observation is worth theorizing about?
2. No phenomenon ever, scientific or not, can be guaranteed to be stable in the face of all 'unknown' factors. They are unknown, you cannot make any statement about that.
I understand where you are coming from, but that puts you right in the middle of the philosophical quagmire mentioned in my earlier comment. If you mean 'variation in people performing the experiment' by those 'unknown factors' then essentially you are making the assumption that the people are not a factor that is expected to influence the result. As such, even the same team repeating the experiment would suffice. Anyway, you get the point.